It has about 600 homes at beach level on the northern end of the city. They include some of San Diego County’s most expensive properties, including a home owned by Kim Fletcher, a member of one of San Diego’s pioneering families who lives with his wife in a beachfront house on land his grandfather bought in the 1940s.

But rising sea levels are putting the Pacific perilously close to those low-lying homes. As a result, the state Coastal Commission says all cities must devise a plan that addresses the inevitable decline of the shoreline.

One of the strategies the state is pushing is something called "managed retreat." The concept calls for abandoning land threatened by coastal erosion, removing any structures such as houses or seawalls, and allowing the beach to return to its natural state.

It is an option that is not sitting well with residents of the small community, such as the 90-year-old Fletcher.

“If you lose the houses on the beach, you’re going to flood everything back to the railroad tracks,” Fletcher said. “The topography is terrible.”

Homeowners worry that their property values would plummet, insurance rates would skyrocket, and mortgages would be harder to obtain if word gets out that the city is considering retreat. Instead, they say, the city should find more ways to pump sand onto its eroding beaches.

Much more popular with Del Mar residents is the idea of sand replenishment, which has been used for years to fortify beaches along the San Diego County coast.

“We want to stress that beach nourishment and sand replenishment .. is the best sea-level rise adaptation strategy,” said Jon Corn, an attorney for Del Mar property owners.

He and his 30 or more clients in the newly formed Del Mar Beach Preservation Coalition were pleased to see that the city had deleted the retreat strategy from the latest version of its sea-level rise adaptation strategy that was released last week, he said. The proposed strategy is expected to go to the City Council for approval in February, and to the California Coastal Commission next summer.

“We are very happy with the direction that it’s taken,” Corn said.

Residents strongly opposed the retreat option when it was discussed over the summer at meetings of the city’s Sea-Level Rise Stakeholder Technical Advisory Committee. As a result, the committee decided to exclude that strategy from the plan.

“The city has many options available,” Lee said. “Retreat is a costly choice. The best option is sand replenishment and sand replacement.”

The Coastal Commission requires all cities on the coast to develop strategies for adapting to rising sea levels.

Mid-range predictions call for the average sea level to rise 5 inches by 2030 in Del Mar, 12 inches by 2050 and more than 3 feet by 2100, according to a draft report released by the city last week.

The prediction is based on averages, so flooding and destructive waves are much more likely to occur during high tides and storm surges.

Most of San Diego County’s coastal communities are built atop or behind sandstone bluffs 60 to 80 feet tall or more. Except for a relative few homes at the edge of the bluff-tops, those communities are not immediately threatened by sea-level rise, so the idea of managed retreat has been less of an issue for them.

Del Mar is different. It has hundreds of low-lying homes on the northern end of the city, south of the outlet of the San Dieguito River.

The average annual income in those households is $102,664 and the average property value is $3.5 million, according to the city’s report. Homes facing the beach average more than $10 million each, and one sold several years ago for $35 million, setting a record for San Diego County.

Some of those homes date to the 1920s and ‘30s. Almost all were built before the Coastal Act was passed in 1976, which limits development on vulnerable coastal lands. The Fletchers’ home on Sandy Lane was built in 1951 for $10,000, Kim Fletcher said.

Along with sand replenishment, strategies for adapting to rising sea levels include seawalls, which are widespread in San Diego County, and elevating structures on stilts or posts, a practice more common on the East Coast. Retreat is generally considered a last resort.

Still, the Coastal Commission and environmental groups such as the Surfrider Foundation recommend managed retreat be considered among the possible strategies.

Each option has its downside. Seawalls have been shown to contribute to shoreline erosion, and the Coastal Commission discourages their use. Sand replenishment is costly and temporary, and likely to be less effective as sea levels continue to rise. Many environmentalists see retreat as the only logical long-term solution.

A Coastal Commission representative this week declined to comment on the Del Mar decision.

“For now, we are monitoring the situation, but we do plan on providing more formal comments before the city takes any final action,” said commission Public Information Officer Noaki Schwartz.

Surfrider policy manager Julia Chunn-Heer said retreat needs to be considered as an option in Del Mar.

“I don’t think sticking our head in the sand is going to do anyone any favors,” Chunn-Heer said.

“Beach nourishment is a great first option, and hopefully that will work,” she said. “But that may not be enough, so we want to have all the tools on the table.”

No one wants anybody to lose their home, she said. But science shows sea levels will continue to rise, probably at a more rapid rate in the future, and there could come a time when hard choices must be made.

One of the retreat options sometimes discussed is for a city or other public agency to buy the private beachfront property, lease the structures or rent them as vacation property until the purchase costs are recovered, then demolish the buildings before the ocean destroys them.

Retreat will be considered for a few low-lying public facilities, the Del Mar report states. Those include the city fire station and nearby public works yard, both on Jimmy Durante Boulevard near the San Dieguito River, that could be moved to higher ground.

Coastal Del Mar homeowner Laura DeMarco said that won’t work for private property, where the owners have no higher ground to move to. Also, the high property values limit potential buyers.

“It works in areas where there is a lot less development,” said DeMarco, a Del Mar resident for 30 years.

Only about 80 of the 600 low-lying homes in Del Mar are beachfront property, she said. Most of the homes are east of the beach tightly packed in a sort of bowl that’s several feet lower than the beachfront properties, most of which are protected by 10- to 15-foot seawalls.

“Those walls protect not just the (beachfront) structures themselves, but everything behind them,” DeMarco said. Rising sea levels or even powerful winter storms have the potential to turn the residential neighborhood into a swamp.

Yet DeMarco and many of her neighbors prefer to take an optimistic view of rising sea levels, noting there is a wide range of possibilities over the years ahead.

“I don’t think anyone is denying it,” she said of climate change and the resulting rise in sea levels. “But the magnitude is in dispute.”

Beach erosion is largely a man-made issue, she said, the result of inland development that blocks the flow of sand down rivers and streams, and the creation of artificial harbors and jetties that disturb the coastal ocean currents.

For decades now, there have been local and regional efforts to pump sediment from harbors, lagoons and offshore deposits to replace what’s lost from the beaches as the result of coastal and upstream development. DeMarco said it’s time to pick up the pace.

“We can do other things to improve the beach and capture more sand,” she said.

For example, sand excavated from inland construction projects could be trucked to the shore and used to beef up the beaches.

Del Mar’s neighbors to the north, Solana Beach and Encinitas, are working together on a U.S. Army Corps of Engineers-led sand replenishment project that will widen their beaches by as much as 50 feet in Encinitas and 150 feet in Solana Beach over the next 50 years. The federal government is paying 65 percent of the costs, estimated at more than $135 million over the life of the project, with the rest of the money from state and local governments.